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Janie - 05 Jun 2004 07:06 GMT

Can anyone tell me why this code doesn't work right on some number
import java.io.*;

class countmoney
public static void main (String[] args) throws IOException

BufferedReader stdin = new BufferedReade
(new InputStreamReader(System.in))
// declares three integer
double amount, sum;// declares a number that can have decimal

System.out.print ("Amount? ")
System.out.flush();

// read a line, and then converts it to an intege
amount=Double.parseDouble(stdin.readLine())

int remainingAmount = (int)(amount*100)

// Find the number of one dollar

int numOfOneDollars = remainingAmount/100

remainingAmount = remainingAmount%100

// Find the number of quaters in the remaining amoun

int numOfQuarters = remainingAmount/25

remainingAmount = remainingAmount%25

// Find the number of dimes in the remaining amoun

int numOfDimes = remainingAmount/10

remainingAmount = remainingAmount%10

// Find the number of nickels in the remaining amoun

int numOfNickels = remainingAmount/5

remainingAmount = remainingAmount%5

// Find the number of pennies in the remaining amoun

int numOfPennies = remainingAmount

// Display result

if (numOfOneDollars == 1)
System.out.println(numOfOneDollars + "--Dollar")

else if (numOfOneDollars > 1)
System.out.println(numOfOneDollars + "--Dollars")

if (numOfQuarters == 1)
System.out.println(numOfQuarters + "--Quarter")

else if (numOfQuarters > 1)
System.out.println(numOfQuarters + "--Quarters")

if (numOfDimes == 1)
System.out.println(numOfDimes + "--Dime")

else if (numOfDimes > 1)
System.out.println(numOfDimes + "--Dimes")

if (numOfNickels == 1)
System.out.println(numOfNickels + "--Nickel")

else if (numOfNickels > 1)
System.out.println(numOfNickels + "--Nickels")

if (numOfPennies == 1)
System.out.println(numOfPennies + "--penny")

else if (numOfPennies > 1)
System.out.println(numOfPennies + "--pennies")

} // method mai
}
It doesn't work on 29 cents it say it has 1 quarter and 3 pennies. 57 cents says 2 quarters 1 nickel and 1 penny. 58 cents has 2 quarters 1 nickel and 2 pennies. 1.13 has 1 dollar 1 dime and 2 pennies. 1.14 has 1 dollar 1 dime and 3 pennies. 1.15 has 1 dollar 1 dime and 4 pennies. 1.16 has 1 dollar 1 dime and 1 nickel. Does anyone see a pattern here?

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Lars-Inge T?nnessen - 05 Jun 2004 14:47 GMT

Hi Janie,

Please use float instead of double. ("float" and "int" are both 32 bits, "double" is 64 bits in Java. These are the sizes the
numbers "occupy" inside the computer)

float amount = (float)0.29;

> double amount, sum;// declares a number that can have decimals
> amount=Double.parseDouble(stdin.readLine());

Regards,
Lars-Inge T?nnessen
www.larsinge.com

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Janie - 05 Jun 2004 19:46 GMT

thank you so much you are so great all of you

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Bruno Jouhier [MVP] - 05 Jun 2004 18:17 GMT

This is because you are using "floating point" numbers.
Floating point numbers represent powers of 2 (even negative ones) exactly
but don't represent all powers of 10 exactly.
So, when you write:
double amount = 0.29;
amount is not "exactly" 0.29, it is close to 0.29 - 3.55e-17.

To test this, you can just execute:
System.out.println("delta=" + (0.29 * 100 - 29.0));
you will get:
delta=-3.5527136788005009E-15

So, when you execute (int)(amount * 100), you obtain 28 rather than 29
because amount * 100 is a bit less than 29, and then you get one cent less
than what you would expect.

To fix this, you can just replace the (int) cast by a call to Math.round:

(int)(amount * 100) => 28
Math.round(amount * 100) => 29

Bruno.

> Can anyone tell me why this code doesn't work right on some numbers
> import java.io.*;
[quoted text clipped - 83 lines]
> }
> It doesn't work on 29 cents it say it has 1 quarter and 3 pennies. 57 cents says 2 quarters 1 nickel and 1 penny. 58 cents has 2 quarters 1

nickel and 2 pennies. 1.13 has 1 dollar 1 dime and 2 pennies. 1.14 has 1
dollar 1 dime and 3 pennies. 1.15 has 1 dollar 1 dime and 4 pennies. 1.16
has 1 dollar 1 dime and 1 nickel. Does anyone see a pattern here?

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Janie - 05 Jun 2004 19:46 GMT

Bruno, Thank you you really are a most valuable person Thanks

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